1. Field of the Invention
The present invention is generally related to methods and systems for generating fluid jets, and more particularly, to a high-pressure fluid system and method for generating thin fluid jets.
2. Description of the Related Art
Fluid jets have been used to clean, cut, or otherwise treat substrates by pressurizing and focusing jets of water or other fluids up to and beyond 100,000 psi and directing the jets against the substrates. The fluid jets can have a variety of cross-sectional shapes and sizes, depending on the particular application. For example, the jets can have a relatively small, round cross-sectional shape for cutting the substrates. The jets can instead have a larger, and/or non-round cross-sectional shape for cleaning or otherwise treating the surfaces of the substrates.
Some systems that generate the high-pressure fluid jet, mix water and abrasives in a mixing chamber before the jet exits the system from a downstream fluid jet exit tube. Typically, in cutting and machining applications, it is desirable to minimize a kerf width at which the fluid jet can cut or machine a material. Kerf width generally refers to the width at which the fluid jet can cut or machine a part or material.
One drawback of conventional fluid jet systems, especially abrasive fluid jet systems (i.e., systems that form the jet from a mixture of abrasives and water) is that they typically cannot cut or machine at a kerf width of less than 0.015 inches. Fluid jet exit tube materials with bores having a diameter less than 0.015 inches are generally not commercially available, and even if available, using such fluid jet exit tubes typically requires extremely accurate fluid jet alignment. Achieving the required accuracy level is not likely possible with conventional fluid jet nozzle designs because the mixing chamber of most existing nozzles is not designed or optimized for use with fluid jet exit tubes with a diameter of less than 0.015 inches.
One reason is that generally a distance from the fluid jet-forming orifice to the fluid jet exit tube entry in existing systems is relatively large, which allows jet spreading (i.e., a widening of the fluid jet between the orifice and the fluid jet exit tube before entry into the fluid jet exit tube). Furthermore, small-bore diameter fluid jet exit tubes require feeding finer and/or dry abrasives; however, finer abrasives are difficult to feed consistently and tend to clog at least a portion of the system.
Another disadvantage of systems that use dry abrasives is that they require conditioning of the exiting liquid-abrasive mixture to substantially completely dry the mixture in order to recycle it back into the system. The conditioning process is time-consuming and therefore, typically, recycling systems are not adapted to recycle the abrasives in-situ.
To prevent clogging, some conventional fluid jet systems feed abrasive slurries into the system; however, these systems generally suffer from poor nozzle suction and inefficient slurry acceleration. The inefficiency of the slurry acceleration in conventional systems is due to the fluid jet being required to accelerate the water in the slurry in addition to the abrasives therein. The inefficient slurry acceleration also subjects the system to substantial component wear and reliability problems because the system uses additional energy to accelerate the water that forms part of the slurry. Such systems may require additional pumps to assist in accelerating the slurry, which in turn requires additional pump controls to maintain pressure.
Other conventional solutions include eductors that receive a fluid jet exit tube and have one abrasive feed channel that extends into the eductor and integrates with the fluid jet exit tube bore, from which the high-pressure liquid-abrasive mixture exits the system. The high-pressure liquid jet also enters the fluid jet exit tube, mixing with the abrasives inside the fluid jet exit tube bore as they travel therethrough.
Since in these systems the high-pressure liquid and abrasives mix only when they travel through the fluid jet exit tube, the space in which the two mix is limited, which may result in inadequate mixing and limited choice of abrasive form. The abrasives used in these systems typically are either dry abrasives or slurries, which exhibit the problems discussed above.
Accordingly, there is a need for a fluid jet system and method that machines or cuts at a kerf width of less than 0.015 inches, exhibits efficient abrasive acceleration, substantially prevents clogging in the system, and does not require substantially drying the abrasives when recycling.